The dramatic increase in the prevalence of overweight and obesity during the past two decades among adults in the United States is related to increased cardiovascular disease, hypertension, dyslipidemia, diabetes, and other chronic diseases. With 63.9% of working-age adults employed, worksites are targets for prevention and intervention programs to control overweight and obesity. The proposed intervention is to use elementary schools as a worksite location for such a program. The proposed intervention leverages the strengths of a school-based worksite by targeting a population that is social, has access to common physical facilities, has low annual turnover rates, and is representative of a significant part of the United States labor force. The primary aim of the proposed program, ACTION!, is to reduce mean body weight by 3.0 kg (BMI by 1.0 kg/m2). Secondary aims relate to both changes at the individual level and at the environmental level. The intervention will address the two major determinants of overweight and obesity: physical activity and diet. A School Wellness Committee at each site will be instrumental in identifying and implementing components of the intervention. Proposed programs will make use of existing resources at the school site. We will also provide additional equipment and programs to meet the recommendations of the Wellness Committees. The program will be evaluated at several levels including formative and process evaluation, collection of cardiovascular risk factor data, questionnaires, and collection of eating and physical activity data. At the conclusion of the main trial, the program will be disseminated to schools in the Greater New Orleans area, and materials will be developed to further disseminate the program to interested schools nation-wide.